松本市北方安曇平における地震探査

概要

論文の詳細を見る
An explosion seismic prospecting was performed in the Azumi Basin, Nagano Prefecture, in spring of 1966 as one of the studies of "Upper Mantle Project". The Matsumoto-Azumi Basin is a Graben-like depression filled with thick Quaternary gravel beds. The Itoigawa-Shizuoka Tectonic Line is concealed beneath the Quaternary beds. The purposes of this prospecting are to clarify the structures of velocity layers in this area and also to detect the position and nature of the Itoigawa-Shizuoka Tectonic Line. Results obtained are as follows. (1) Five velocity layers are found in this area: 1st layer 1. 2〜1.5 km/sec, 2nd layer 2.6 km/sec, 3rd layer 3.0〜3.4 km/sec 4th layer 3.8〜4.2 km/sec (partly 3.3 km/sec) 5th layer 6.4 (?) km/sec. (2) The maximum thickness of the Quaternary gravel beds is about 360 m including 1st and 2nd velocity layers in the central part of the basin. (3) The Itoigawa-Shizuoka Tectonic Line is detected as a low velocity part about 600 m wide beneath the Quaternary gravel beds between the National Railway Oito Line and the Route 147 in the north of Toyoshina Town.
日本地質学会の論文
1976-12-30